The present invention relates to control devices and, more particularly, to photocontrol devices and methods of calibrating the same.
Photocontrol devices are used in a variety of applications where it is desirable to provide a control signal responsive to detection of a light level. One common application of such photocontrol devices is in the detection of ambient light levels. In particular, to detect that transition from daylight to night so that lights may be turned on for security, safety and/or aesthetic reasons. For example, street lights are generally provided with photocontrol devices to turn on the street lights at dusk. An example of such a photocontrol device is the Model 2000 series of photocontrols available from Tyco Electronics Corporation.
Because of the variability typically found in sensing devices such as photocontrol devices, they are generally calibrated before and/or after installation. Such calibration typically includes adjusting the sensitivity of a photosensor circuit included in the photocontrol device so that it activates a switch at a desired light level. The switch may be, for example, a relay in the photocontrol device that provides power to turn on a light when the detected light level drops below a selected level. Known approaches to adjusting the sensitivity of the photocontrol device to calibrate the photocontrol device include changing a calibration resistor coupled to the photosensor, providing a rotary mounted photosensor and/or changing the size of an aperture/window of the photocontrol device through which the photosensor receives light. Each of these approaches may increase the cost of the photosensor device and/or the difficulty of the calibration process.